Typically, fossil fuel furnaces and other appliances employ the use of a high pressure combustion blower in order to supply pressurized air to various locations within a heating and ventilation system. These furnaces typically comprise a sealed combustion air system with a blower arrangement at the outlet of the furnace that creates a pressure differential so that a selected amount of air may be directed through secondary heat exchangers and to and from remote vent locations with the use of piping having a relatively small diameter. Accordingly, a constant relatively high air pressure and flow must be maintained for proper mixing and combustion of the fuel air mixture. It is desirable to achieve this goal using a compact blower assembly which is capable of fitting within limited available space, and which operates with a minimum power input to a drive motor.
Inasmuch as the pressure of the blower assembly fan wheel is proportional to the peripheral speed thereof, prior attempts of achieving constant high pressure outputs have increased the diameter of the fan wheel in order to increase the pressure output. Other approaches have utilized blower systems with increased power input in order to boost the speed of the fan wheel. These approaches require increased system cost, and have resulted in problems in installation since all the necessary system components must be fit within limited available space. In addition, the overall system efficiency is reduced due to the increased motor power input.
Other attempts to increase the pressure output in blower assemblies have provided particular baffling arrangements. For example, U.S. Patent 4,549,848 to Wallman describes a curved inlet baffle that is utilized in conjunction with a conventional spiral-type blower housing and fan wheel arrangement. The baffle in this so-called "Swirlwind" arrangement is positioned relative to an axial inlet of the blower housing at an angle less than 90 degrees to the inside surface of the blower housing. In addition, this baffle design includes a straight edge piece located along the side proximate the cutoff point of the blower housing. This design results in a significant undercut which cannot be practically molded as an integral part of the blower surface side surface, thus requiring a multiple piece assembly. Likewise, internal turbulence developed within this arrangement produces objectionable noise levels. Furthermore, these known arrangements are less efficient than the present invention, as is shown in the table in the Detailed Description of the Preferred Embodiment.